A known electrophotographic image forming apparatus includes a main body casing, and process cartridges detachably attachable to the main body casing.
In the above image forming apparatus, the main body casing includes a pair of left and right frames made of resin, a pair of left and right metal frames fixed to inner surfaces of the left and right frames made of resin, and four pipes extending between the metal frames. The process cartridges each include a photosensitive drum extending in the left and right direction. The process cartridges are disposed between the pair of petal frames when attached to the main body casing.
In the image forming apparatus, to maintain the rigidity in the main body frame, the process cartridges are detachably attachable to the main body casing in substantially a top-bottom direction (which is a direction perpendicular to an axial direction of the photosensitive drum). In this configuration, it is difficult to detachably attach the process cartridges relative to the frame member along an axial direction of the process cartridges.